90-14-02 BOEING: Amendment 39-6644. Docket No. 90-NM-13-AD. \n\n\tApplicability: All Model 737-300 and 737-400 series airplanes, certificated in any category. \n\n\tCompliance: Required within the next 12 months after the effective date of this AD, unless previously accomplished. \n\n\tTo prevent inadvertent rudder trim resulting in unacceptably increasing the level of pilot effort required to maintain the correct heading during takeoff, which may result in a rejected takeoff, accomplish the following: \n\n\tA.\tReplace the rudder trim control knob with a smooth rounded fluted knob approved by the Manager, Seattle Aircraft Certification Office, FAA, Transport Airplane Directorate. \n\n\tB.\tIf the rudder trim control knob is located near the rear of the cockpit center console, add a guard rail with a height of approximately 1.5 inches to the rear of the cockpit center console if no rail is currently installed, or, if a rail is currently installed, raise the cockpit center console rearrail to a height of approximately 1.5 inches, in accordance with procedures approved by the Manager, Seattle Aircraft Certification Office, FAA, Transport Airplane Directorate. \n\n\tC.\tAn alternate means of compliance or adjustment of the compliance time, which provides an acceptable level of safety, may be used when approved by the Manager, Seattle Aircraft Certification Office (ACO), FAA, Northwest Mountain Region. \n\n\tNOTE: The request should be submitted directly to the Manager, Seattle ACO, and a copy sent to the cognizant FAA Principal Maintenance Inspector (PMI). The PMI will then forward comments or concurrence to the Seattle ACO. \n\n\tD.\tSpecial flight permits may be issued in accordance with FAR 21.197 and 21.199 to operate airplanes to a base in order to comply with the requirements of this AD. \n\n\tThis amendment (39-6644, AD 90-14-02) becomes effective on August 6, 1990.